With the advent of the microprocessor and related sophisticated electronic controls, vehicular ignition systems and ignition system strategies have undergone a great many improvements. Among these, more efficient burning of combustion gases, better control of vehicle timing and ignition timing have all played an important part in improving fuel economy, extending the percentage of exhaust gas recirculation, increasing power and improving other performance characteristics.
Changes in the ignition coil design have also been a part of this overall improvement. Use of the single ignition coil for each ignition device, i.e. spark plug, has provided the opportunity to more precisely control ignition characteristics within each combustion chamber. However, almost without exception, these strategies evolve around a single ignition per combustion event. Beyond the timing of the ignition event, combustion efficiency has depended in large part on the combustion chamber design, including measures for increasing combustion gas swirl prior to ignition, and similar techniques.
In addition, limited use has been made in an ignition strategy involving "re-striking" the ignition generator during the same ignition event. In other words, the spark plug has been caused to fire multiple times during each combustion cycle, and provided the engine is operating below a predetermined speed, e.g. 1200 RPM. At engine speeds above the predetermined level, the ignition coil and thus the ignition device itself would fire but once per conventional practice.
One known system using a re-strike strategy includes use of an electronic distributorless ignition system (EDIS) having two coils adapted to distribute ignition voltage to each of four combustion chambers, and known as a four-tower-type coil pack. Such a coil pack is fairly large, having to (i) provide ignition to each of the two cylinders for each combustion event of the engine and (ii) accommodate for performance losses across the spark plug leads. Re-strike rapidity or the timing capability of a coil has been noted to be directly proportional to coil size, that is the size, weight and number of turns or windings to the primary and secondary coils. Consequently, with the four-tower EDIS system previously known, the re-strike strategy did not incorporate all re-strikes within the initial stages of the combustion event, nor was the significance of such a strategy realized until the present invention.